LeetCode Solutions

LeetCode-0001.js

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    /**
     * Map number to its position.
     */
    const map = {
        [nums[0]]: 0
    }

    const l = nums.length

    for (let i = 1; i < l; i++) {
        const current = nums[i]
        const diff = target - current
        const dest = map[diff]

        if (dest !== undefined) {
            return [dest, i]
        } else {
            map[current] = i
        }
    }
};

LeetCode-0002.js

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function(l1, l2) {
    let head = { val: undefined, next: null }
    let current = head
    let incremental = false

    // Merge two array.
    while (l1 || l2 || incremental) {
        const val1 = l1 ? l1.val : 0;
        const val2 = l2 ? l2.val : 0;
        const val = val1 + val2 + (incremental ? 1 : 0)
        
        incremental = val >= 10;
        current.next = { val: val % 10, next: null }
        current = current.next
        l1 = l1 ? l1.next : null;
        l2 = l2 ? l2.next : null;
    } 

    return head.next
};

LeetCode-0003.js

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
    if (!s) return 0

    // Letter and the last index
    const map = {
        [s[0]]: 0
    }

    const l = s.length

    let max = 1
    let headIndex = 0
    let currentLength = 1

    for (let i = 1; i < l; i++) {
        const currentLetter = s[i]
        const lastIndex = map[currentLetter]
        
        if (lastIndex !== undefined && lastIndex >= headIndex) {
            headIndex = lastIndex + 1
            currentLength = i - headIndex + 1
            map[currentLetter] = i
        } else {
            currentLength += 1
            map[currentLetter] = i
            
            if (currentLength > max) {
                max = currentLength
            }
        }
    }

    return max
};